package com.example.myfirstapp.util;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

import android.animation.Animator;
import android.animation.AnimatorListenerAdapter;
import android.animation.ValueAnimator;
import android.graphics.Rect;
import android.view.MotionEvent;
import android.view.VelocityTracker;
import android.view.View;
import android.view.ViewConfiguration;
import android.view.ViewGroup;
import android.widget.AbsListView;
import android.widget.ListView;

public class SwipeListViewTouchListener implements View.OnTouchListener {
	// Cached ViewConfiguration and system-wide constant values
	private int mSlop;
	private int mMinFlingVelocity;
	private int mMaxFlingVelocity;
	private long mAnimationTime;

	// Fixed properties
	private ListView mListView;
	private OnSwipeCallback mCallback;
	private int mViewWidth = 1; // 1 and not 0 to prevent dividing by zero
	private boolean dismissLeft = true;
	private boolean dismissRight = true;

	// Transient properties
	private List<PendingSwipeData> mPendingSwipes = new ArrayList<PendingSwipeData>();
	private int mDismissAnimationRefCount = 0;
	private float mDownX;
	private boolean mSwiping;
	private VelocityTracker mVelocityTracker;
	private int mDownPosition;
	private View mDownView;
	private boolean mPaused;

	/**
	 * The callback interface used by {@link SwipeListViewTouchListener} to inform its client
	 * about a successful swipe of one or more list item positions.
	 */
	public interface OnSwipeCallback {
	    /**
	     * Called when the user has swiped the list item to the left.
	     *
	     * @param listView               The originating {@link ListView}.
	     * @param reverseSortedPositions An array of positions to dismiss, sorted in descending
	     *                               order for convenience.
	     */
	    void onSwipeLeft(ListView listView, int [] reverseSortedPositions);

	    void onSwipeRight(ListView listView, int [] reverseSortedPositions);
	}

	/**
	 * Constructs a new swipe-to-action touch listener for the given list view.
	 *
	 * @param listView The list view whose items should be dismissable.
	 * @param callback The callback to trigger when the user has indicated that she would like to
	 *                 dismiss one or more list items.
	 */
	public SwipeListViewTouchListener(ListView listView, OnSwipeCallback callback) {
	    ViewConfiguration vc = ViewConfiguration.get(listView.getContext());
	    mSlop = vc.getScaledTouchSlop();
	    mMinFlingVelocity = vc.getScaledMinimumFlingVelocity();
	    mMaxFlingVelocity = vc.getScaledMaximumFlingVelocity();
	    mAnimationTime = listView.getContext().getResources().getInteger(
	            android.R.integer.config_shortAnimTime);
	    mListView = listView;
	    mCallback = callback;
	}

	/**
	 * Constructs a new swipe-to-action touch listener for the given list view.
	 * 
	 * @param listView The list view whose items should be dismissable.
	 * @param callback The callback to trigger when the user has indicated that she would like to
	 *                 dismiss one or more list items.
	 * @param dismissLeft set if the dismiss animation is up when the user swipe to the left
	 * @param dismissRight set if the dismiss animation is up when the user swipe to the right
	 * @see #SwipeListViewTouchListener(ListView, OnSwipeCallback, boolean, boolean)
	 */
	public SwipeListViewTouchListener(ListView listView, OnSwipeCallback callback, boolean dismissLeft, boolean dismissRight) {
	    this(listView, callback);
	    this.dismissLeft = dismissLeft;
	    this.dismissRight = dismissRight;
	}

	/**
	 * Enables or disables (pauses or resumes) watching for swipe-to-dismiss gestures.
	 *
	 * @param enabled Whether or not to watch for gestures.
	 */
	public void setEnabled(boolean enabled) {
	    mPaused = !enabled;
	}

	/**
	 * Returns an {@link android.widget.AbsListView.OnScrollListener} to be added to the
	 * {@link ListView} using
	 * {@link ListView#setOnScrollListener(android.widget.AbsListView.OnScrollListener)}.
	 * If a scroll listener is already assigned, the caller should still pass scroll changes
	 * through to this listener. This will ensure that this
	 * {@link SwipeListViewTouchListener} is paused during list view scrolling.</p>
	 *
	 * @see {@link SwipeListViewTouchListener}
	 */
	public AbsListView.OnScrollListener makeScrollListener() {
	    return new AbsListView.OnScrollListener() {
	        @Override
	        public void onScrollStateChanged(AbsListView absListView, int scrollState) {
	            setEnabled(scrollState != AbsListView.OnScrollListener.SCROLL_STATE_TOUCH_SCROLL);
	        }

	        @Override
	        public void onScroll(AbsListView absListView, int i, int i1, int i2) {
	        }
	    };
	}

	@Override
	public boolean onTouch(View view, MotionEvent motionEvent) {
	    if (mViewWidth < 2) {
	        mViewWidth = mListView.getWidth();
	    }

	    switch (motionEvent.getActionMasked()) {
	        case MotionEvent.ACTION_DOWN: {
	            if (mPaused) {
	                return false;
	            }

	            // Find the child view that was touched (perform a hit test)
	            Rect rect = new Rect();
	            int childCount = mListView.getChildCount();
	            int[] listViewCoords = new int[2];
	            mListView.getLocationOnScreen(listViewCoords);
	            int x = (int) motionEvent.getRawX() - listViewCoords[0];
	            int y = (int) motionEvent.getRawY() - listViewCoords[1];
	            View child;
	            for (int i = 0; i < childCount; i++) {
	                child = mListView.getChildAt(i);
	                child.getHitRect(rect);
	                if (rect.contains(x, y)) {
	                    mDownView = child;
	                    break;
	                }
	            }

	            if (mDownView != null) {
	                mDownX = motionEvent.getRawX();
	                mDownPosition = mListView.getPositionForView(mDownView);

	                mVelocityTracker = VelocityTracker.obtain();
	                mVelocityTracker.addMovement(motionEvent);
	            }
	            view.onTouchEvent(motionEvent);
	            return true;
	        }

	        case MotionEvent.ACTION_UP: {
	            if (mVelocityTracker == null) {
	                break;
	            }

	            float deltaX = motionEvent.getRawX() - mDownX;
	            mVelocityTracker.addMovement(motionEvent);
	            mVelocityTracker.computeCurrentVelocity(500); // 1000 by defaut but it was too much
	            float velocityX = Math.abs(mVelocityTracker.getXVelocity());
	            float velocityY = Math.abs(mVelocityTracker.getYVelocity());
	            boolean swipe = false;
	            boolean swipeRight = false;

	            if (Math.abs(deltaX) > mViewWidth / 2) {
	                swipe = true;
	                swipeRight = deltaX > 0;
	            } else if (mMinFlingVelocity <= velocityX && velocityX <= mMaxFlingVelocity
	                    && velocityY < velocityX) {
	                swipe = true;
	                swipeRight = mVelocityTracker.getXVelocity() > 0;
	            }
	            if (swipe) {
	                // sufficent swipe value
	                final View downView = mDownView; // mDownView gets null'd before animation ends
	                final int downPosition = mDownPosition;
	                final boolean toTheRight = swipeRight;
	                ++mDismissAnimationRefCount;
	                mDownView.animate()
	                        .translationX(swipeRight ? mViewWidth : -mViewWidth)
	                        .alpha(0)
	                        .setDuration(mAnimationTime)
	                        .setListener(new AnimatorListenerAdapter() {
	                            @Override
	                            public void onAnimationEnd(Animator animation) {
	                                performSwipeAction(downView, downPosition, toTheRight, toTheRight ? dismissRight : dismissLeft);
	                            }
	                        });
	            } else {
	                // cancel
	                mDownView.animate()
	                        .translationX(0)
	                        .alpha(1)
	                        .setDuration(mAnimationTime)
	                        .setListener(null);
	            }
	            mVelocityTracker = null;
	            mDownX = 0;
	            mDownView = null;
	            mDownPosition = ListView.INVALID_POSITION;
	            mSwiping = false;
	            break;
	        }

	        case MotionEvent.ACTION_MOVE: {
	            if (mVelocityTracker == null || mPaused) {
	                break;
	            }

	            mVelocityTracker.addMovement(motionEvent);
	            float deltaX = motionEvent.getRawX() - mDownX;
	            if (Math.abs(deltaX) > mSlop) {
	                mSwiping = true;
	                mListView.requestDisallowInterceptTouchEvent(true);

	                // Cancel ListView's touch (un-highlighting the item)
	                MotionEvent cancelEvent = MotionEvent.obtain(motionEvent);
	                cancelEvent.setAction(MotionEvent.ACTION_CANCEL |
	                        (motionEvent.getActionIndex()
	                                << MotionEvent.ACTION_POINTER_INDEX_SHIFT));
	                mListView.onTouchEvent(cancelEvent);
	            }

	            if (mSwiping) {
	                mDownView.setTranslationX(deltaX);
	                mDownView.setAlpha(Math.max(0f, Math.min(1f,
	                        1f - 2f * Math.abs(deltaX) / mViewWidth)));
	                return true;
	            }
	            break;
	        }
	    }
	    return false;
	}

	class PendingSwipeData implements Comparable<PendingSwipeData> {
	    public int position;
	    public View view;

	    public PendingSwipeData(int position, View view) {
	        this.position = position;
	        this.view = view;
	    }

	    @Override
	    public int compareTo(PendingSwipeData other) {
	        // Sort by descending position
	        return other.position - position;
	    }
	}

	private void performSwipeAction(final View swipeView, final int swipePosition, boolean toTheRight, boolean dismiss) {
	    // Animate the dismissed list item to zero-height and fire the dismiss callback when
	    // all dismissed list item animations have completed. This triggers layout on each animation
	    // frame; in the future we may want to do something smarter and more performant.

	    final ViewGroup.LayoutParams lp = swipeView.getLayoutParams();
	    final int originalHeight = swipeView.getHeight();
	    final boolean swipeRight = toTheRight;

	    ValueAnimator animator;
	    if (dismiss)
	        animator = ValueAnimator.ofInt(originalHeight, 1).setDuration(mAnimationTime);
	    else
	        animator = ValueAnimator.ofInt(originalHeight, originalHeight - 1).setDuration(mAnimationTime);


	    animator.addListener(new AnimatorListenerAdapter() {
	        @Override
	        public void onAnimationEnd(Animator animation) {
	            --mDismissAnimationRefCount;
	            if (mDismissAnimationRefCount == 0) {
	                // No active animations, process all pending dismisses.
	                // Sort by descending position
	                Collections.sort(mPendingSwipes);

	                int[] swipePositions = new int[mPendingSwipes.size()];
	                for (int i = mPendingSwipes.size() - 1; i >= 0; i--) {
	                    swipePositions[i] = mPendingSwipes.get(i).position;
	                }
	                if (swipeRight)
	                    mCallback.onSwipeRight(mListView, swipePositions);
	                else
	                    mCallback.onSwipeLeft(mListView, swipePositions);

	                ViewGroup.LayoutParams lp;
	                for (PendingSwipeData pendingDismiss : mPendingSwipes) {
	                    // Reset view presentation
	                    pendingDismiss.view.setAlpha(1f);
	                    pendingDismiss.view.setTranslationX(0);
	                    lp = pendingDismiss.view.getLayoutParams();
	                    lp.height = originalHeight;
	                    pendingDismiss.view.setLayoutParams(lp);
	                }

	                mPendingSwipes.clear();
	            }
	        }
	    });

	    animator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
	        @Override
	        public void onAnimationUpdate(ValueAnimator valueAnimator) {
	            lp.height = (Integer) valueAnimator.getAnimatedValue();
	            swipeView.setLayoutParams(lp);
	        }
	    });

	    mPendingSwipes.add(new PendingSwipeData(swipePosition, swipeView));
	    animator.start();
	  }
	}
